A rear projection type projector (rear projector) or a head-up display (HUD) has been known as a projection type display apparatus in which image light is generated using a light source generating coherent light, such as a laser diode, and the image light is projected on a screen. Either of the rear projector and the HUD uses an image light projection screen on which the generated image light can be projected, that is, a so-called transmission type screen. For example, the rear projector uses a transmission type screen so that the image light can be recognized from a side opposed to the light source. On the other hand, in the HUD, the image light transmitted by the transmission type screen is reflected by a combiner so that the image light can be recognized.
To make it possible for human beings to recognize image light projected on a screen, the screen must have a certain level of scattering performance with respect to incident light.
To this end, in the transmission type screen, a random concavity and convexity shape such as frosted glass is often provided in the surface of the screen where an image is projected. Thus, incident image light is diffused.
However, when such a transmission type screen is irradiated with coherent light such as laser light, an interference pattern of the laser light caused by the random structure appears on the projection surface. The interference pattern is called a speckle pattern or a speckle noise. Thus, there is a problem that a clear image cannot be reproduced.
As a technique for reducing the speckle noise caused by the transmission type screen, for example, Patent Document 1 discloses a configuration in which a micro-lens array portion including a plurality of unit lenses arrayed two-dimensionally in a matrix is provided in at least one surface of a translucent substrate.
In addition, Patent Document 2 discloses a transmission type screen including a random phase difference layer in which a plurality of first regions and a plurality of second regions are formed irregularly within a surface of the layer so that incident light can be divided into two linearly polarized components perpendicular to each other, and the linearly polarized components can be emitted.